Throw an exception in the soft button manager if two buttons have the same name

[NicoleYarroch]

Bug Report

Currently in the SDLSoftButtonManager, if two buttons have the same name, an error is logged. We should instead throw an exception since the soft buttons will be removed from the display because the soft button property is set to an empty array.

Reproduction Steps

1. Create two soft button objects with the same name. Send the soft buttons using the screen manager.

Expected Behavior

An exception should be thrown.

Observed Behavior

An error is logged and the softButtonObjects property is set to an empty array.

OS & Version Information

• iOS Version: n/a
• SDL iOS Version: 7.0
• Testing Against: n/a